Manufacture of vesicular glass



Aug- -1 194,4- f. J. H. Fox Erm. 2,354,807

l MANUFACTURE oF vEsIcLR GLASS,

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MANUFACTURE oF vnslcuLAR GLAss 3v sheets-sheet' 5 loriginal Filednec. 24, 1957 #Trae/'ver kPatented Aug. 1, 1944 2,354,807 y MANUFACTURE oF vEsIcULAR GLASS John H. Fox, Pittsburgh, and William 0. Lytle, New Kensington, Pa., assignors to Pittsburgh IPlate Glass Company,l a. corporation of Penn- Sylvania Original application December 24, 1937, Serial No.

181,630, now Patent No. 2,261,022, dated October 28 1941. Divided and this application May 15, 19h, seria1No.393,54s

3 Claims.

The present invention relates to the manufacture of glass products and it has particular relation to the manufacture of a porous glass product suitable for use as a means for heat and sound insulation and` as a light weight building material. l

One object of the invention is to provide an v apparatus for manufacturing porous glass in which operation is substantially continuous and involves a minimum expenditure of labor.

This and other objects will be apparent from consideration of the following specification and claims.

A. It has heretofore been proposed to introduce bubbles of gas into molten glass in order to form a cellular product Iwhich is an insulating medium for heat and sound. The conventional method of preparing the product involved the provision of a portion of molten glass containing bubbles of gas or containing a gas-producing inaterial in molds and then allowing the molten or plastic material to expand to ll the mold. Obviously, a substantial amount of labor is involved in such operation which tends to increase the cost of the product.

According to the provisions of the present invention this objection is obviated by forming a foam or froth of molten or plastic glass in a'suitable container by any convenient method, for example, by blowing molten glass with air or other gas or by whipping molten glass and then drawing olf the froth from the top of the mass as a continuous sheet and then cooling the sheet and cutting it up into blocks or units of suitable size.

Embodiments of apparatus suitable for use in practicing the invention are disclosed in the drawings in which Figures l and 3 are crossmolten state ows from the melting tank through a passage 44 below the lower edge of the baille 4I into the drawing compartment 43, and may be converted into froth or foam by any suitable means. For purposes of illustration there vis shown a feeder mechanism for the introduction of calcium carbonate, vermiculite or similar gasproducing or gas-containing substances through the bottomof the compartment into the stream of glass as it enters the drawing compartment.

. may be introduced into the chamber by means of.

This feeder mechanism comprises an inlet conduit 46 extending through the bottom of the compartment 43 and being provided with a screw conveyor 41, for forcing the solid gassng material into the molten glass. The tube is connected at its lower end to tle throat 48 of an air lock chamber`49, constituting means for preventing gases generated by decomposition of the calcium carbonate at the ,bottom of the drawing compartment from escaping through the tube. `'I'his chamber is connected by means of a throat 5| with a conventional hopper `52. Slide'valves 53 and 54 disposed respectively in the throats 5I and 48 constitute means for maintaining positive pressure in the chamber. Air under compression a conduit 56 to assist in forming bubbles in the mass and to prevent any tendency of the molten glass to percolate downwardly through the granular material in tube 46. If preferred the latter tendency may be obviat'ed by elevation of the rear end of screw 41 and tube 46 in such manner that the rear ends thereof are above the level of the glass. If desired the foam may be produced entirely by means of a gassing medium such as air, steam, or the like introduced in fluid form through the conduit 56, or if preferred the foaming may be produced solely by means of a solid material such as calcium carbonate which is introduced by the action of a screw 41.

Screw 41 projects at its lower end through a suitable packing (not shown) in the lower extremity ofthe tube 46 and is driven vby any convenient means, for example by means of a worm gear 51 engaging a motor actuated worm 58.

The temperature of the glass in the drawing compartment 43 may be controlled by'means of electrical heating devices, by tubes for conducting heating or cooling'gases in heat exchange relation with the molten mass, or by any other suitable means. In the drawingsl are shown a series of electrodes 59, placed at suitable points adjacent to the bottom of the compartment. The temperature of the mass adjacent to the surface is controlled by means of tubes 6I through which a heating or cooling medium may be circulated as required. These tubes may be provided with outlets for the further gasification of the molten mass.

Transverse feeding of the molten material at the surface of the mass for purposes' of drawing it out in sheet form is obtainedlby means of a conveyor or chain 62 composed of relatively re fractory material and trained about rollers 63 and 64, the latter of which is rotated by suitable means (not shown). The conveyor is provided at suitable intervals withvblades 66 extending outwardly therefrom and projecting along the lower reach of the conveyor below the surface of molten material in the compartment 43. Conveyor 62 extends outwardly over the forward edge of the compartment 43 in proximity to one extremity of a second conveyor 61 which is trained about rollers 88,. driven by suitable means (not shown). This conveyor, constitutes means for carrying away the vesicular mass of glass as it is forced out of the drawing compartment by the conveyor 62 and preferably extends through an annealing lehr (not shown). A third conveyor 69 is disposed above and in parallelism to the conveyor 61 at a suitable height to press or restrict the foamy mass upon the conveyor 61 to a desired thickness.

In the operation of this embodiment of the invention molten glass is allowed to flow into the drawing compartment 43 from tank 42 and while it is passing through the throat or channel 44 calcium carbonate or other suitable gassing agent is extruded into the stream. The viscous bubbly mass rises in the drawing chamber or forehearth until it is enmeshed between the paddles 66 upon conveyor 52. The latter then forces the surface layer out upon conveyor 61 where it is allowed to solidify and is then annealed and cui; up into slabs of convenient dimensions.

In Figure 2 is shown an embodiment of apparatus for forming the vesicular sheet into blocks as it is drawn from the tank or chamber. In this embodiment of apparatus, a suitable melting chamber in the form of a tank or compartment 10, corresponding substantially to the drawing compartment 43 in Figure 1 is provided for receiving the batch which includes the bubble-forming material. Feeding mechanism Ei for supplying the batch to the chamber 'E0 comprises an inlet conduit |12 which communicates through an opening |13 into the bottom of the chamber it and which is provided with a screw conveyor A15 for forcing the ingredients of the lmixedbatch into the melting chamber. Suitable driving gearing 16 rotates the screw conveyor' from the lower end thereof and the lower end of the conduit is provided with a bearing head or end wall |11 which rotatably supports the lower end portion of the screw conveyor.

A hopper itil has a lower throat portion |32 communicating with the lower end portion of the conduit |12 and has a central air lock chamber id communicating at opposite extremities with the lower throat portion |82 andA an upper flaring mouth |85 in which the batch material is supplied. Suitable slide valves |86 and |81 disposed yat the upper and lower extremities, respectively, of the air lock chamber prevent back pressure from forcing any of the material rearwardly or upwardly through the throat portion |82. These valves can be opened alternately in order that the glass-making ingredients can be received into the chamber |83, and to permit such ingredients to be fed through the throat portion |82 into the conduit |12 from which they are forced into the melting chamber 10.

A conduit |88 communicating with the air lock chamber |84 and with a suitable source (not shown) of iluid or gas under pressure is provided to facilitate the passage of the batch through the conduit |12 into the melting chamber 10 and also to facilitate the forming of a foamy batch in the melting chamber.A y

'I'he melting of the materials to proper conposed below the lower reach of the upper conveyor and these' two conveyors preferably extend through a lehr 16 in which the glass is annealed and cooled down to a temperature suitable for handling. These conveyors are respectively provided with cleats or lugs 11 and 18 which coact to cut or mold-the sheet of glass into blocks of appropriate size as it is formed. It will be noted that the roller at the forward end ofthe upper conveyor is spaced a sufficient distance above the sistency in the chamber Il is effected by means of electrical heating devices. such as electrodes mounted at suitable locations in 'an intermediate portion oi the chamber. The portion of the batch adjacent its upper surface is controlled by means of tubes |42 through whichheating or cooling medium can be circulated as required. -These .tubes manche provided with outlets maidethe' lower conveyor to disengage the blades or lugs on the upper conveyor from the blocks before the latter reach the end of travel thereof. The rearward extremity of the upper conveyor is held in proximity to the lower conveyor by means of a roller The operation of this form of the invention is identical with that of the form disclosed in Figure l except that the glass is melted or softened or formed in the drawing chamber and the sheet as it is drawn out and while still plastic is scored or cut into blocks.

A mixture of crushed glass and CaCO: may be introduced through the hopper mouth and feeding conduit |12 into the melting chamber 10 where the glass melts down and the calcium carbonate decomposes to form bubblesI of CO2. If the lime, sand and soda ash of the batch are introduced in this way the CO2 evolved will be entrapped in the molten glass as it seeks to escape upwardly to form the cellular mass without introduction of additional gassing agents. In the event that the cellular body is formed by heating a mixture of crushed glass and calcium carbonate, a glass of the composition of ordinary sheet glass may be employed. It should be so crushed or broken up that it will pass through a 28 mesh screen, but it is retained by a 100 mesh screen. Such material will sinter at about 1300 or 1400" F. and will flow as apasty plastic mass at a temperature of about 1600 to l750 F. At highe'r temperatures it melts down completely. Preferably it is formed or bloated into a cellular mass while in this intermediate, plastic state. Within this temperature range the particles of glass, although they weld together at the points of contact, they do not completely coalesce or flow together. The resultant sheet apparently contains -voids resulting from incomplete fusing of the particles and also from liberation of the gas bubbles in the mass. 'The apparent density of this mass may be varied almost at will, butfor rial may be easily cut and sawed and can be nailed without breaking.

0f course the cellularmass could be formed under such conditions that the particles will be completely fused together to form a. bubbly mass. and such mode of operation is contemplated as being within the scope of the present invention.

In the form of the invention disclosed in Figure 3 a tank I5 is provided with a drawing compartment I6 separated therefrom by a baille I1 all of which respectively correspond to tank 4I, drawingoompartment 43 and baille 4| in the form of the invention disclosed in Figure 1. Molten glass in the drawing compartment is converted into a froth orfoam by means of a gas or a gas-forming liquid introduced through inlets 08 which are vsupplied from a conduit 8,9. A suitable agitator for thoroughly distributing the bubbles of glass may be provided and includes a lshaft 90 which is land further by means of tubes 9B for heating or cooling gases disposed at suitable elevations in the tank. Additional gassing'medium for further increasing the porosity of the molten glass may be introduced through a conduit 99 having inlets extending through the forward wall f the drawing tank adjacent to the point where thel glass is drawn from the tank. l

The upper edge of the forward wall of the compartment terminates in a lip |02 designed to discharge the surface portion of the foamy mass of molten glass outwardly under a smoothing or compressing rollers |03 upon a suitable conveyor which may comprise a series of driven rollers or preferably s shown in the drawings a conveyor chain |04 trained about supporting and driving roller |05 and leading to a suitable annealing lehr (not shown). i

For purposes of insuring the uniform feed of the molten glass from the drawing compartment to the conveyor |04 a suitable pusher mechanism may be provided. An example of such mecha- ,nism includes a horizontal rod |06 which is provided at its forward end with a blade |01 adapted to dip below the surface of the molten mass.

This rod projects rearwardly through a slot |08 in the rear wall of the drawing compartment and is supported upon and actuated by a pair of parallel cranks |09 which are secured upon and driven by shafts The shafts in turn are journaled in bearings in a support ||2. A blast of air for cooling the surface of the molten glass in the drawing compartment is supplied through a conduit ||3 disposed above the rod |06.

The mode of operation of this embodiment of the inventionis substantially the same as that of the form disclosedgin Figure l. Molten glass flows from the tank 85 into the drawing compartment 86 and is transformed into a foam by gas or gas-forming liquid such as water which is introduced through the inlets 88 and 9 I. The temperature of the mass is suitably regulated by means of the electrodes 91 and the tubes 98. The surface of the `mass is quickly cooled by means of a blast of air from the conduit ||3, in order to rendery it sufficiently viscous to retain the bubbles.. The rotation of the shafts causes the rod |06 to travel downwardly to dip the blade |01 into the surface of the mass and then to travel forwardly to push a portion of the material outwardly over the lip |02 and upon the con'- veyor |04. lSubsequently continued rotationof the shafts causes'the pusher rod to 'rise to lift the blade |01 fromthe glass and then to retract to the initial drawing position. The foamy mass 4upon the conveyor |04 is carried forwardly through the annealing lehr for purposes of relieving the interiial strains upon the glass.

In any o'f the embodiments of the invention disclosed in Figures 1, 2 and 3, the devices'for expediting the flow of glass from the drawing hearth may be eliminated, and'ow of glassout upon the conveyors 61, 16 and |04 obtained by gravity alone and/or by the pull of the conveyor i upon the cellular mass. Conveyor rollers `arranged at suitable intervals are considered as the equivalents of the continuous conveyors disclosed.

The present process may be employed in the formation of cellular glass weighing upto 75 or 80 pounds per cubic foot.

- This is a division of my copending 'applica-- tion Serial No. 181,630,1iled December 24, 1937,

since issued on October 28, 1941,v as Patent No. 2,261,022.-

Although only the preferred forms of the invention have been shown and described, it

, receive and carry away the molten will be apparent to those skilled in the art that numerous modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.

What we claim is:

1. Apparatus for preparing cellular` glass coinprising a chamber adapted to contain fused glass and having a discharge opening for cellular glass formed in a wall thereof, means to feedv fused glass and a foam-producing ingredient below the surface of fused glass in the chamber, an impeller disposed in the chamber abovethe molten foam and being provided with paddle means prolecting into said molten foam and being movable substantially horizontally in the uppel DOIOII 0I the mOlten-OBJII, in Order SUC- cessively to eject portions of the latter outwardly through the discharge opening and a conveyor disposed contiguous to the discharge opening to receive and carry away the cellular glass as it is formed.

2. Apparatus lfor preparing cellular glassl comprising a receptacle for a pool of molten glass, means -for feeding molten glass upwardly m the receptacle, means for-introducing a foamproducing ingredient into the lower portion of carry the foam in successive portions andto.

eject vthe portions from the compartment and conveyor means external of the receptacle to receive and-carry away the portions as they are ejected.

3. An apparatus forpreparing cellular glass comprising a chamber adapted to contain fused glass and having a wall with a discharge lip over which the fused glass is adapted to be discharged, meansfor feeding glass and a foamproducing ingredient below the surface of the fused glass in the chamber, an impeller disposed in the chamber above the fused glass and being provided with'paddle means projecting into the molten foam and being movable substantially horizontally in the upper portion of the molten foam in order to successively eject portions of the latter outwardly over the lip and a conveyor disposed contiguous to the discharge opening to foam as it is elected over the lip.

JOHN H. FOX. WIILIAM 0. LYTLE. 

